The compound 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]sulfinyl]-1H-benz imidazole, having the generic name omeprazole, is a proton pump inhibitor, i.e. effective in inhibiting gastric acid secretion, and is useful as an antiulcer agent. In a more general sense, omeprazole may be used for treatment of gastric-acid related diseases in mammals and especially in man.
Omeprazole and therapeutically acceptable salts thereof, are described in EP 5 129. This patent also discloses a process for the preparation of omeprazole and other structurally related substituted benzimidazoles.
U.S. Pat. No. 5,386,032 describes an improved process for synthesis of omeprazole. This process describes the oxidation step and a work-up procedure for omeprazole. The oxidation step utilizes m-chloroperoxybenzoic acid in a solvent system consisting of an organic solvent and an aqueous phase of constant pH. The work-up procedure includes an extraction step and precipitation of omeprazole by the addition of an alkyl formate to the aqueous phase.
Another alternative process for the manufacture of omeprazole is described in U.S. Pat. No. 5,391,752. This process utilizes magnesium monoperoxyphtalate as an oxidizing agent.
Omeprazole is a sulfoxide and a chiral compound, withthe sulfur atom being the stereogenic center. Thus, omeprazole is a racemic mixture of its two single enantiomers, the R and S-enantiomer of omeprazole. An enantioselective process for the synthesis of the single enantiomers of omeprazole is described in WO 96/02535. The asymmetric oxidation utilizes a chiral titanium complex to induce the chirality.
In the light of the above there was still a need for a new convenient and more efficient process for the manufacture of racemic omeprazole.